I would suggest not limiting it to chemistry. In my perfect world, the next incarnation of the Joker would brilliant engineer and inventory more broadly, because my preferred next version of the Joker is "the Anti-Batman": an individual driven by tragedy to achieve extraordinary heights of genius, willpower, and courage. Just with a radically, catastrophically different ideology. Whereas Bruce seeks to impose order on the malicious chaos of the world around him, the Joker seeks to control the chaos, to ride it like a tiger. Its not about an ideological drive to encourage others to believe in anarchy ( that's the Ledger version ), but a personal belief that the world is chaos, and that they are personally suited for thriving in such an environment. This Joker doesn't care about what others believe, except insofar as it makes them vulnerable or amuses him. He's selfish and, technically, rational, but also profoundly whimsical; power is about being able to do what you want, even if what you want is absurd. . . because you have the power.
Or basically, Batman is a genius prodigy vigilante, who's end goal is to transform Gotham into a just and happy place. The Joker is a genius prodigy crimelord, who's end goal is to rule Gotham, and transform it into a place where he, the Joker, can do whatever the hell he wants.
( If you want to imagine Aiden Gillan in clown makeup, feel free. "Chaos is a ladder" is a great philosophy in Gotham City. )